The present invention generally relates to bleed air systems and, more specifically, to a system and method of using a variable geometry ejector for a bleed air system which utilizes a minimal amount of high-pressure air, thus improving the overall engine cycle performance. This is accomplished through the use of a variable ejector using downstream pressure feedback to control the flow and pressure.
The present invention generally relates to bleed air systems within engines and more specifically to a variable geometry ejector for a bleed air system using integral bleed pressure feedback. The present invention may be used in any gas turbine engine and is particularly well suited for vehicles and aircraft.
Bleed air systems are used for many purposes within gas turbine engines including supplying auxiliary power, cooling air, and off design component matching. Regardless of the purpose bleed air must be sufficiently high pressure to insure a proper flow through the system. Bleed air is extracted after it has been compressed which requires extra work by the engine. Therefore, extra fuel consumption is always associated with gas turbine compressor bleed air, which does not produce power or thrust. Bleed air requirements can drastically reduce engine performance by robbing the engine of high pressure air that could be used to burn fuel and make power.
U.S. Pat. No. 4,711,084 discloses an ejector assisted compressor bleed for use in a gas turbine engine having multiple compressor stages. Bleed air is extracted through multiple apertures in the shroud of a low pressure compressor stage and collected in a reservoir surrounding the bleed apertures of the shroud. A supply passage directs bleed air from the reservoir to the desired component. An ejector nozzle is positioned in the supply passage to introduce a high pressure primary flow into the passage and draw, as a secondary flow, the relatively low pressure bleed air from the reservoir. The nozzle obtains its high pressure air from a high pressure stage of the compressor. It is the nature of an ejector that only a relatively minor amount of high pressure bleed air is needed to power the low pressure bleed system. When the engine is operating at design speeds, generally the bleed system will not need the ejector power and the high pressure supply can be shut down. The ""084 patent controls the primary stream flow rate with the primary stream pressure. The primary stream pressure is a function of the engine design or characteristic. While such a system represents a significant advancement in the art, a variable device is needed that controls the downstream pressure while not being dependant on engine characteristics.
U.S. Pat. No. 4,631,004 issued to Mock discloses an actuator operatively connected with the control valve to selectively control flow of the motive fluid in accord with a pressure difference between the motive fluid and a selected and possible variable reference pressure. However it does not consider the possibility of using integral ejector downstream pressure feedback to control the ejector primary flow and ejector exit pressure.
As can be seen there is a need for an improved apparatus and method that is easily adaptable to a multitude of different engine types and provides a bleed system which utilizes a minimal amount of high-pressure air, thus improving the overall engine cycle performance.
The present invention is directed to a variable geometry bleed system using integral bleed pressure feedback which utilizes a minimal amount of high-pressure air, thus improving the overall engine cycle performance and is easily adaptable to a multitude of different engine types.
One aspect of the invention is a system for bleeding air from a compressor in an engine comprising a primary inlet, a secondary inlet, a variable geometry ejector, a mixing section, a diffuser with an upstream end and a downstream end, and a tube comprised of a diffuser feedback port and an actuator port. The diffuser feedback port may be in communication with the downstream end and the actuator port may be in communication with an ejector needle valve actuator. The ejector needle valve actuator may be comprised of a piston, at least one spring, and a vent. The needle is attached to the piston and extends into a nozzle area of the valve. There may be a first seal ring interposed between the ejector needle valve actuator and piston. There may also be a second seal ring interposed between the ejector needle valve actuator and the needle. The nozzle area may be annular. High pressure air may be introduced to the primary inlet. The needle, actuated by the piston, sets the nozzle area of the valve to control the high pressure flow-rate into a mixing section. Low pressure air may be led from the secondary inlet to the mixing section and allowed to mix with the high pressure nozzle flow forming a ejector exit mixed flow. The ejector exit mixed flow may be drawn from the upstream end of the diffuser to the downstream end of diffuser and allowed to flow through an opening and a diffuser feedback port. Air drawn through the diffuser feedback port may be drawn through the tube to the actuator port and introduced to the ejector needle valve actuator. As such, the downstream pressure feedback may be used to control the nozzle geometry to maintain an almost constant ejector exit pressure that is independent of the ejector flow-rate.
According to another aspect of the present invention, a system for bleeding air from a compressor in an engine is disclosed comprising a primary inlet, a secondary inlet, a variable geometry ejector, a mixing section, a diffuser with an upstream end and a downstream end, a tube comprised of a diffuser feedback port, and an actuator port. The diffuser feedback port may be in communication with the downstream end and said actuator port may be in communication with an ejector needle valve actuator. The ejector needle valve actuator may be comprised of a piston, two springs, and a vent. There may be a first seal ring interposed between the ejector needle valve actuator and piston. There may also be a second seal ring interposed between the ejector needle valve actuator and the needle. The needle is attached to the piston and extends into a nozzle area, wherein high pressure air introduced from said primary inlet at a flow between 0 and 30 ppm and a pressure between 10 and 200 psig is contained. The needle, actuated by the piston, sets the nozzle area of the valve to control the high pressure flow-rate into a mixing section, wherein low pressure air which may be led from the secondary inlet at a flow between 0 and 30 ppm and pressure between 0 and 40 psig to the mixing section and allowed to mix with the high pressure nozzle flow forming a ejector exit mixed flow. The ejector exit mixed flow may be drawn from the upstream end of the diffuser to the downstream end of diffuser and allowed to flow through an opening to a prioritization valve, NBC system and the diffuser feedback port, wherein air drawn to the diffuser feedback port may be drawn to the actuator port and introduced to the ejector needle valve actuator.
According to a further aspect of the present invention, an apparatus for bleeding air from a compressor in an engine is disclosed comprising a primary inlet, a secondary inlet, a variable geometry ejector, a mixing section, a diffuser with an upstream end and a downstream end, a tube comprised of a diffuser feedback port and an actuator port. The diffuser feedback port may be in communication with said downstream end and the actuator port may be in communication with an ejector needle valve actuator. The ejector needle valve actuator may be comprised of a needle attached to a piston, two springs, and a vent. The needle and piston may extend into a nozzle area, wherein high pressure air may be introduced from the primary inlet at a flow between 0 and 30 ppm and a pressure between 10 and 200 psig, wherein the needle, actuated by the piston, sets the nozzle area of the valve to control the high pressure flow-rate into a mixing section, wherein low pressure air which is led from said secondary inlet at a flow between 0 and 30 ppm and pressure between 0 and 40 psig to said mixing section and allowed to mix with said high pressure nozzle flow forming a ejector exit mixed flow. There may be a first seal ring interposed between the ejector needle valve actuator and piston. There may also be a second seal ring interposed between the ejector needle valve actuator and the needle. The ejector exit mixed flow is varied integrally according to the piston, and pressure of air introduced into the primary inlet and secondary inlet. The ejector exit mixed flow is drawn from the upstream end of the diffuser to the downstream end of diffuser and allowed to flow through an opening to a prioritization valve, NBC system and the diffuser feedback port, wherein air drawn to said diffuser feedback port may be drawn to the actuator port and introduced to the ejector needle valve actuator. This may be accomplished and varied integrally.
In another aspect of the present invention, a method for bleeding air from a multi-stage compressor in an engine is disclosed. This method may be comprised of allowing high pressure air to flow through a primary inlet to a nozzle area, wherein a portion of a piston is contained. The needle, actuated by the piston, sets the nozzle area of the valve to control the high pressure flow-rate into a mixing section. Low pressure air may be introduced to a secondary inlet and allowed to flow from the secondary inlet to the mixing section. The high pressure nozzle flow may be mixed with low pressure air to create ejector exit mixed flow with a pressure between the high pressure nozzle flow and low pressure air. The ejector exit mixed flow may be allowed to flow from the upstream end of the diffuser to the downstream end of the diffuser, wherein a portion of ejector exit mixed flow may be introduced to a diffuser feedback port and the remainder may be allowed to flow to an opening. The portion of ejector exit mixed flow that may be introduced to said diffuser feedback port may be drawn through a tube to the actuator port of the tube and introduced to an ejector needle valve actuator, wherein the piston is contained and a vent. The position of the piston is controlled by the difference in force created by springs in communication with said piston and the static pressure of the ejector exit mixed flow introduced through said actuator port to ejector needle valve actuator.